REZINOMOTORNAYA HELICOPTERThe model we offer you to make, made by rare scheme — two bearing rotor during rotation intersect. To build it is not very difficult — especially as the engine are well-known modelers rubber tubing. Energy stored in them when you twist, enough to fly a small model of this type. The diameter of the rotor is 600 mm, and each of them has its own shaft, both rotating in opposite directions, which provides a synchronizing mechanism. Four gears cut from metal gears with a suitable external diameter, which you can pick up from parts of an old alarm clock or a broken clockwork toy. After processing, the thickness of each gear should be about 2 mm, the diameter of inner hole is 2 mm.

The housing in which are mounted the shafts of the rotors and the synchronizing mechanism, cut and bent sheet of aluminum with a thickness of 0.5 mm. rotor Shafts from steel wire Ø 2 mm; they can also be made of a knitting needle of suitable thickness. Mount gears to shafts — steel pins Ø 0.8 mm holes for them first serverlists in gears, but directly in the Assembly process and in the shafts of the rotors.
Bushings rotors — aluminum. The blades are cut from balsa plates 2 mm thick and fixed to the sleeve with glue. After gluing the rotors need to be balanced.
The fuselage and tail boom are made of foam — preferably from packaging. Landing gear and skids — made of aluminum with a thickness of 0.5 mm; they are glued to the fuselage with epoxy. A vertical shaft for the rubber bands (each of them contains 16 threads of circular cross section) should be strengthened by a tube of heavy paper.
Fig. 1. Rezinomotornaya twin-rotor helicopter
Fig. 1. Rezinomotornaya twin-rotor helicopter:
1 — the fuselage (foam), 2 — chassis 3 — balancing the rod with a sinker, a 4 — clock mechanism, 5 — rotor, 6 — tail.

When building models, note: be sure to clear coordination of the position of the rotors. If the blades of the left rotor is parallel to the line of flight, right blade should be perpendicular to it. The blades of both rotors are installed under the same angle, otherwise the flight will be non-linear. If she turns right, for example, it means that the angle of the blades of the right rotor more than the left. In the end the lifting force of the right rotor is greater than the left, which entails a reversal of the model.
To adjust flight designed slim balance shaft mounted in the forward fuselage. Moving brass or steel weight, you can ensure that the helicopter flew forward, hovering in place or even moving backwards.
Fig. 2. The sequence of manufacturing of gears synchromesh mechanism
Fig. 2. The sequence of manufacturing of gears synchromesh mechanism:
A — drilling the pinion hole Ø 0,8 mm for pins; B — cutting the gear; The gear ready.

Fig. 3. Manufacturer reference mechanism
Fig. 3. The production of clock mechanism:
A — scan of the body (the figure shows the schematic scan, in accordance with the existing gears, its size should be specified on the site and made a template from thick paper, move it to the dimensions of the dural plate with thickness of 0.5 mm); B — one of the stages of construction of the body (note that the holes for the axis synchronizing gear is cut together); to ensure the accuracy of the location of the shafts easy to use plasam drawn on thick paper.

Sending a model in the first flight, to start install the rotor 10-15 revolutions. The helicopter needs to fly, dodging to the left slightly. Increasing the degree of twist of the rubber motor, don’t forget to move the balancing weight forward. The recommended degree of twist amounts to about 100 rpm.

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